Process
OCR A-Level Chemistry H432
Foundations in Chemistry
Topic overviewAtomic structure, isotopes and counting sub-atomic particlesRelative isotopic, atomic, molecular and formula massPredicting ionic charges and the common ionsWriting formulae, balanced equations and ionic equationsThe mole, molar mass and the Avogadro constantEmpirical and molecular formulae, and hydrated saltsGas volumes, concentration and the ideal gas equationStoichiometry, percentage yield and atom economyApparatus, and why high atom economy mattersMathematical skills and measuring mass, volume and gasAcids, alkalis, dissociation and neutralisationPreparing a standard solutionCarrying out a titration and its calculationsPlanning an experiment: variables, apparatus and recording resultsPractical safety, heating and filtrationUncertainty, percentage error, precision and accuracyEvaluating results: anomalies, conclusions, limitations and improvementsAssigning oxidation numbersRoman numerals in names, and the chlorate and nitrate ionsOxidation, reduction and metals reacting with acidsRedox equations and identifying what is oxidisedShells, orbitals and sub-shellsThe order in which sub-shells fillWriting electron configurations for atoms and ions
Bonding and Structure
Topic overviewIonic bonding and the properties of ionic compoundsCovalent and coordinate bondingLone pairs, bonding pairs and average bond enthalpyElectron pair repulsion theory, linear and trigonal planar shapesTetrahedral, pyramidal and non-linear shapes and their bond anglesOctahedral shapes, ions, and drawing molecules in three dimensionsElectronegativity, polar bonds and polar moleculesPermanent and induced dipoles, and hydrogen bondingSimple molecular lattices and why they melt easilySolubility and conductivity of simple molecular compounds
Periodic Table and Energy
Topic overviewPeriodicity and the electron configurations of periods 2 and 3The blocks, and first and successive ionisation energiesMetallic and giant covalent structures and their propertiesGroup 2 reactions with oxygen, water and acidsIonisation energy down Group 2 and the alkalinity of the hydroxidesUses of Group 2 compounds in agriculture and medicineThe halogens: boiling points, London forces and reactivityHalogen displacement reactions and the colours seenDisproportionation and the chlorination of waterTesting for halide ions with silver nitrate and ammoniaTesting for carbonate, sulfate and halide ionsTesting for ammonium ions and the order of the testsConcentration, pressure and measuring reaction rateCatalysts and their industrial importanceThe Boltzmann distribution, temperature and catalysts
Enthalpy Changes
Topic overviewExothermic and endothermic reactions and enthalpy profilesStandard conditions and the standard enthalpy changesBond enthalpies, q = mcΔT and calorimetryCalculating enthalpy change from bond enthalpiesWhy average bond enthalpies give only an approximationHess' law and enthalpy cycles from combustion and formation dataWorking through an enthalpy cycle and the sign conventionsCalorimetry and correcting for heat loss
Chemical Equilibrium
Basic Concepts of Organic Chemistry
Topic overviewIUPAC nomenclature and the alkyl groupsGeneral, structural, displayed and skeletal formulaeHomologous series, functional groups and saturationStructural isomers, bond fission and curly arrowsChain, position and functional group isomerismCurly arrows, homolytic and heterolytic fissionNucleophiles, electrophiles, radicals and the mechanism steps
Core Organic Chemistry
Topic overviewAlkanes: bonding, shape and boiling pointsCombustion of alkanes and their reaction with halogensThe radical substitution mechanism and its limitationsAlcohols: polarity, solubility and classificationOxidation, dehydration and substitution reactions of alcoholsHydrolysis of haloalkanes and comparing the ratesNucleophilic substitution and carbon-halogen bond strengthCFCs, radicals and the catalytic destruction of ozoneCombining analytical techniques to identify a compound
Alkenes
Topic overviewAlkenes: the double bond, sigma and pi bonding, and shapeE/Z and cis-trans isomerism in alkenesHydrogenation, halogenation and hydration of alkenesElectrophilic addition, carbocation stability and Markownikoff's ruleAddition polymerisation and repeat unitsWaste polymers, and biodegradable and photodegradable alternatives
Organic Synthesis
How Fast?
Topic overviewRate equations, order and the rate constantDeducing orders and finding the units of kWhat the rate equation reveals about the mechanismConcentration-time graphs and continuous monitoringHalf-life and the rate constant of a first-order reactionRate-concentration graphs and the initial rates methodClock reactions, colorimetry and analysing kinetic graphsThe rate-determining step and testing a proposed mechanismTemperature, the rate constant and the Arrhenius equationThe ln k against 1/T graph and finding the activation energy
Physical Chemistry and Transition Elements
Topic overviewMole fraction, partial pressure and ICE tablesKc and Kp expressions, their units and calculationsWhat changes the equilibrium constant, and the reaction quotientLattice enthalpy and the Born-Haber cycleEnthalpy of solution and hydration, and the effect of ionic charge and sizeEntropy and calculating entropy changeGibbs free energy and thermodynamic feasibility
Acids, Bases and Buffers
Topic overviewBrønsted-Lowry acids and bases and their reactionsKa, pKa, pH and the ionic product of waterCalculating the pH of strong acids, strong bases and weak acidspH and hydrogen ion concentrationWhat a buffer is and how it resists a change in pHBuffer calculations and the buffer that controls blood pHTitration curves, choosing an indicator and using a pH meterpH titration curves for the four acid-base combinationsHow an indicator works and choosing the right one
Redox and Electrode Potentials
Topic overviewOxidising and reducing agents, and balancing half-equationsCombining half-equations and using oxidation numbersRedox titrations and their calculationsStandard electrode potentials and setting up half-cellsThe electrochemical series and predicting feasibilityStorage cells and fuel cells
Transition Elements
Topic overviewLigands, complex ions and coordination numberElectron configurations from Sc to Zn, and which are transition elementsVariable oxidation states, coloured ions and catalysisThe shapes of complexes, stereoisomerism and cisplatinLigand substitution, haemoglobin and the copper complexesHydroxide precipitates of iron, manganese and chromiumRedox interconversions of iron, chromium and copperWhy ligand substitution happens and the changes it causesPrecipitation reactions written as aqua complexesDissolving hydroxides in excess ammonia and distinguishing the ions
Aromatic Compounds
Topic overviewThe delocalised model of benzene and the evidence for itNitration, halogenation and Friedel-Crafts reactions of benzeneThe reactions of phenol, and directing effectsElectrophilic substitution and directing effectsPhenol: acidity, bromination and nitrationWhy phenol is more reactive than benzene, and planning a synthesis
Organic Chemistry and Analysis
Topic overviewOxidation and reduction of carbonyls, and the addition of HCNThe nucleophilic addition mechanism2,4-DNPH and Tollens' reagentCarboxylic acids: solubility and reactions with metals, carbonates and basesEsterification and the hydrolysis of estersAcyl chlorides and their reactions with alcohols, amines and ammoniaAmines as bases, and preparing aliphatic aminesSecondary and tertiary amines, and preparing aromatic aminesAmino acids, their reactions, and amidesOptical isomerism and identifying a chiral centreCondensation polymerisation and the ester and amide linkagesHydrolysing condensation polymers and telling them from addition polymersNitriles from haloalkanes and from carbonyl compoundsFriedel-Crafts reactions and lengthening the carbon chainThin-layer and gas chromatography, Rf values and retention timesTest-tube tests for the organic functional groupsTests for the inorganic ions and interpreting chromatograms
Spectroscopy
Topic overviewCarbon-13 and proton NMR: peaks, chemical shift and integrationSpin-spin splitting and predicting a spectrumTMS, deuterated solvents and the D₂O shakeCombining elemental analysis, mass spectrometry, IR and NMRMolecular formula from the molecular ion, and fragmentation lossesWhat IR and NMR each contribute to a structureInfrared absorption, global warming and breathalysersA systematic approach and the degree of unsaturation
Redox and Electrode Potentials
- 6 subtopics
- 10 things to know
- Components 01 and 03
What Redox and Electrode Potentials covers
Redox written as half-equations, redox titrations, standard electrode potentials and the cells built from them, and where feasibility predictions from E values break down.
Where it is assessed
Components 01 and 03
Periodic Table, Elements and Physical Chemistry, then the unified paper.
Check the OCR specification ↗The 6 subtopics
Each one has its own page.
- Oxidising and reducing agents, and balancing half-equationsRecall questions on what each agent does, and on balancing a half-equation for atoms, oxygen, hydrogen and charge.Open →
- Combining half-equations and using oxidation numbersRecall questions on multiplying and combining half-equations, and on identifying what is oxidised and reduced from oxidation numbers.Open →
- Redox titrations and their calculationsRecall questions on detecting the end point, why manganate(VII) is self-indicating, and using the mole ratio from the balanced equation.Open →
- Standard electrode potentials and setting up half-cellsRecall questions on the definition and standard conditions, why the hydrogen electrode is the reference, the salt bridge, and setting up metal, gas and ion half-cells.Open →
- The electrochemical series and predicting feasibilityRecall questions on what a more positive or more negative E means, calculating cell potential, and why a feasible prediction may not be observed.Open →
- Storage cells and fuel cellsRecall questions on discharge and charging, the lithium fire hazard, what a fuel cell is, and how its operation differs from a storage cell.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
In balancing a half-equation, how do you balance atoms other than oxygen and hydrogen?
Key term
How can you identify which species is oxidised in a redox reaction using oxidation numbers?
Numbers
Why can a single half-cell potential not be measured, which half-cell is the reference, and how is a metal half-cell set up?
Key term
In the electrochemical series, what does a more positive standard electrode potential indicate?
Key term
In the electrochemical series, what does a more negative standard electrode potential indicate?
Numbers
What is a storage cell, how is its EMF calculated, and what reaction occurs at the negative electrode on discharge?
Key term
What is a fuel cell, and what happens at its negative and positive electrodes?
Key term
What instrument is used to measure the cell potential of an electrochemical cell?
Process
Outline the basis and calculation sequence of a redox titration.
Take Redox and Electrode Potentials further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Oxidising agent vs Reducing agent
Oxidising agent: a species accepting electrons and becoming reduced. Reducing agent: a species donating electrons and becoming oxidised.
Anode vs Cathode
Anode: electrode where oxidation occurs. Cathode: electrode where reduction occurs.
Fuel cell vs Storage cell
Fuel cell: a device supplied continuously with fuel and oxidant. Storage cell: a rechargeable device storing reactants within the cell.
Questions from this topic
Each one with the model answer underneath.
- 1
What is an oxidising agent?
Model answer
A species that accepts electrons from another species, causing that species to be oxidised, while the oxidising agent itself is reduced.
- 2
Why does an oxidising agent become reduced during a reaction?
Model answer
Because it accepts electrons from another species, and gaining electrons is the definition of reduction.
- 3
What is a reducing agent?
Model answer
A species that donates electrons to another species, causing that species to be reduced, while the reducing agent itself is oxidised.
- 4
Why does a reducing agent become oxidised during a reaction?
Model answer
Because it loses electrons to another species, and losing electrons is the definition of oxidation.
- 5
In a redox reaction, what happens to the electrons of the reducing agent?
Model answer
The reducing agent loses electrons and is oxidised.
- 6
When constructing a redox equation, how do you write the oxidation half-equation?
Model answer
Write the half-equation showing the species that loses electrons, with electrons appearing on the product side.
What is inside Levo
Six ways to work the same material.
Redox and Electrode Potentials revision questions
- What does Redox and Electrode Potentials cover in OCR A-Level Chemistry?
- 6 subtopics: oxidising and reducing agents, and balancing half-equations, combining half-equations and using oxidation numbers, redox titrations and their calculations, standard electrode potentials and setting up half-cells, the electrochemical series and predicting feasibility and storage cells and fuel cells. Each one has its own page with questions and model answers.
- How is Redox and Electrode Potentials organised?
- By the OCR H432 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Redox and Electrode Potentials, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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